Casting equipment and casting method using same

ABSTRACT

A casting equipment for producing a casting with a large cross-section for a very thick steel material includes: a casting part with a passage for a molten steel for casting the molten steel into a casting; a support part arranged separately from the casting part for receiving and supporting the casting in at least one of the sides of the casting; and a solidifying part arranged outside the casting provided with a first quality control device for solidifying the casting. A casting method includes: preparing a molten steel for casting; casting the molten steel in the casting part with the passage opened or closed into a casting; conveying the casting to the solidifying part; and conveying the solidified casting to a subsequent process so as to improve the quality of the casting, thus increasing substantially the yield rate of castings.

TECHNICAL FIELD

The present invention relates to a casting installation and a castingmethod using the same, and more particularly, to a casting installationthat may easily produce a slab for an extremely thick steel material andenhance quality, yielding percentage, and productivity of the slab andto a casting method using the same.

BACKGROUND ART

In general, an extremely thick steel material has a thickness of atleast 100 mm, and internal quality such as porosity and mechanicalproperties such as impact and toughness of the extremely thick steelmaterial are managed with a thickness reduction ratio (slabthickness/product thickness) limited according to an intended use. Forexample, as marine structural steel, there is required an extremelythick steel material having the thickness reduction ratio of 4 or moreand pressure steel and wind power structural steel requires thethickness reduction ratio of 3 or more.

Currently, an extremely thick steel material may be produced throughpredetermined post-processes such as forging and rolling of an ingot orslab produced by a continuous casting process. When an extremely thicksteel material is produced by the ingot process, i.e., the formermethod, the ingot is produced into an extremely thick steel materialproduct by a forging process or is subject to an additional rollingprocess. In particular, since the extremely thick steel materialrequiring a high thickness reduction ratio regards the internal qualityas an important factor, a slab mostly cast in an ingot is subjected to aforging operation and then produced through a rolling process.

As such, producing an extremely thick steel material by using a slabcast in an ingot may correspond to the production of an extremely thicksteel material having a high thickness reduction ratio and has anadvantage for the production of a small-lot in consideration of a demandcharacteristic of the extremely thick steel material. However, the slabproduced by using the ingot process requires cutting of an unsoundregion for removing the unsound region generated around a riser and amain riser. Thus, deterioration in yielding percentage of the slab iscaused due to cutting of upper and lower regions of the slab, so thatproduction costs for producing the extremely thick steel material isincreased.

Meanwhile, when an extremely thick steel material is produced by thecontinuous casting process, i.e., the latter method, in general, theextremely thick steel material is produced by a method of rolling a slabsubject to a continuous cast. Although the latter method is excellent inyielding process and thus superior to the ingot process in terms ofproduction costs when compared to the ingot process, there is a problemin that a thickness of the extremely thick steel material is alsolimited due to a limited slab thickness when steel products requiring ahigh thickness reduction ratio are produced.

Further, since the extremely thick steel material is relatively thickcompared to a normal slab, it takes a long time until the slab iscompletely solidified after being cast. When a slab for an extremelythick steel material thicker than a general slab produced by a generalcaster is produced by a conventional casting method in which moltensteel is continuous cast and cut, solidification is completed to aninside of the slab and thus the installation of the caster becomes verylong for a cutting process, which leads to enlargement of theinstallation, resulting in consumption of enormous initial cost in termsof production costs.

In addition, since possibility in which an internal defect of the slaboccurs is high compared to an ingot material, there is a highpossibility in which an internal defect in a continuous cast slab mayremain in the extremely thick steel material. In addition, since acontinuous cast installation for producing a slab is optimized for massproduction, there is a disadvantageous problem in terms of production ofa small-lot.

Thus, development of new installation and process is urgently requiredfor producing a slab for extremely thick steel material having a highthickness reduction ratio, the slab being not easy to be produced in ageneral casting installation. That is, required is an installation andprocess which is capable of enhancing internal quality and yieldingpercentage same as or better than an ingot slab in terms of steelquality, is advantageous in producing various kinds of small-lotextremely thick steel materials in terms of production, and is capableof enhancing productivity compared to the production of the ingot slab.

DISCLOSURE OF THE INVENTION Technical Problem

The present invention provides a casting installation easily producing aslab for an extremely thick steel material and to a casting method usingthe same.

The present invention also provides to a casting installation capable ofenhancing quality and yielding percentage of a slab and to a castingmethod using the same.

The present invention also provides to a casting installation capable ofenhancing productivity of a slab and efficiency of a processinstallation and to a casting method using the same.

Technical Solution

A casting installation according to an embodiment of the presentinvention includes: a casting unit defining a passage through whichmolten steel passes and for casting the molten steel into a slab; and asolidification unit including: a support unit disposed spaced apart fromthe casting unit and receiving the slab from the casting unit anddisposed on at least any one place of sides of the slab to support theslab; and a first quality controller provided on an outside of the slabto induce solidification of the slab.

The first quality controller may include: a first stirrer disposed inproximity to an outside of the slab and able to elevate in alongitudinal direction of the slab; a second stirrer provided spacedapart below the first stirrer and able to elevate in the longitudinaldirection of the slab; and a first heater installed so as to be able tomove forward and backward in a region directly above the slab andconfigured to heat an upper portion of the slab.

The first stirrer may have coils wound around the slab and disposed inthe form of a circle.

The casting unit may include: an accommodation unit having a space inwhich the molten steel is accommodated; a drawing machine drawing theslab from the accommodation unit to a lower portion; and a secondquality controller provided on an outside of the passage.

The accommodation unit may include a mold configured to form the passagethrough which the molten steel supplied to a tundish passes, and themold may be formed so that the slab has a thickness of 800 mm or lessand a width of 2000 mm or less.

The second quality controller may include: a stirring unit including atleast one stirrer disposed on an outside of the mold and configured tostir at least any one of the molten steel and unsolidified molten steelinside the slab; a second heater installed so as to be able to moveforward and backward in a region directly below the mold and configuredto heat an upper portion of the slab.

The stirring unit may include: a third stirrer disposed in proximity tothe mold and able to elevate in a drawing direction of the slab; afourth stirrer provided spaced apart below the third stirrer and able toelevate in the drawing direction of the slab.

The third stirrer may have coils wound around the mold or the slab anddisposed in the form of a circle.

A pusher for separating the slab from the drawing machine may beprovided to the casting unit and the pusher may be installed so as to beable to reciprocally move forward and backward toward the solidificationunit.

A transfer unit transferring the slab from the casting unit to thesolidification unit or from the solidification unit to an outside of thesolidification unit may be provided.

A casting method according to an embodiment of the present inventionincludes: providing molten steel to prepare casting; casting the moltensteel in a casting unit allowing a passage through which the moltensteel passes to be opened or closed; transferring a slab producedthrough the casting to a solidification unit; and transferring the slabto a post-process after solidification of the slab is completed.

The casting of the molten steel may be repeated in the casting unitafter the slab is transferred to the solidification unit.

When the casting of the molten steel is repeated, the transferring theslab to the solidification unit may be performed while the molten steelis transferred to the casting unit so that preparing the casting isperformed.

When the casting of the molten steel is a single casting, that is onetime casting, the solidification of the slab may be completed in thecasting unit or after the slab is transferred to the solidificationunit.

The molten steel may be cast at a casting rate 0.3 m per minute or less.

Advantageous Effects

According to a casting installation and a casting method using the sameaccording to embodiments of the present invention, it is possible toimprove yielding percentage of a slab produced by a continuous casting.That is, when a slab cast in a casting unit is solidified in a castingunit or a solidification unit, the length of a pipe generated at anupper portion of the slab is reduced to enhance yielding percentage ofthe slab by delaying solidification of the upper portion of the slab byusing a second heater or a first heater.

In addition, molten steel remaining in a mold is stirred to enhanceinner quality during casting and unsolidified molten steel in slab isstirred after a casting is completed, so that the equiaxed crystal ratioin the slab may be enhanced, segregation and porosity may be reduced,and an internal defect such as a pipe occurring at an edge end of theslab may be reduced.

In addition, according to the present invention, it is possible tocontinuously cast another slab in a casting unit during a process inwhich solidification of a slab is performed in a solidification unit.Thus, since a process required for solidification of an extremely thicksteel material may be completed in the solidification unit, a casting ofmolten steel may not stop, thus capable of improving productivity of aslab and efficiency of a process installation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a view of a casting installation according to anembodiment of the present invention.

FIG. 2 illustrates a flow chart of a casting method according to anembodiment of the present invention.

FIGS. 3A to 3F illustrate views of an operating state of a castinginstallation according to a casting method in FIG. 2.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, specific embodiments will be described in detail withreference to the accompanying drawings. The present invention may,however, be embodied in different forms and should not be construed aslimited to the embodiments set forth herein. Rather, these embodimentsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of the present invention to those skilled inthe art. Like reference numerals refer to like elements throughout.

FIG. 1 illustrates a view of a casting installation according to anembodiment of the present invention. FIG. 2 illustrates a flow chart ofa casting method according to an embodiment of the present invention.FIGS. 3A to 3F illustrate views of an operating state of a castinginstallation according to a casting method in FIG. 2. FIGS. 3A to 3Fillustrate changes in the casting installation working to produce slab.

Referring to FIG. 1, a casting installation 1 as an installation toproduce a slab for an extremely thick steel material according to anembodiment of the present invention includes a casting unit 1 a defininga passage through which molten steel passes and for casting the moltensteel into a slab; and a solidification unit 1 b including: a supportunit 500 disposed spaced apart from the casting unit 1 a and receivingthe slab from the casting unit 1 a and disposed on at least any oneplace of sides of the slab to support the slab; and a first qualitycontroller 600 provided on an outside of the slab to inducesolidification of the slab.

The casting unit 1 a as a section in which continuous casting of refinedmolten steel is carried out includes: an accommodation unit 100accommodating the molten steel; a drawing machine 200 drawing the slabfrom the accommodation unit 100 to a lower portion; and a second qualitycontroller 300 provided on an outside of the passage through which themolten steel passes.

The accommodation unit 100 defines a space accommodating molten steelbefore the casting of the molten steel and includes a ladle 120accommodating molten steel, a tundish 140 receiving the molten steelfrom the ladle 120, and a mold 160 disposed spaced apart below thetundish 140.

The ladle 120 is a container for accommodating molten steel afterrefining is completed and may be produced in various hollow shapeshaving an internal space capable of accommodating the molten steel. Ingeneral, the ladle 120 may be provided in plurality to increase thecirculation rate of a continuous casting installation.

The tundish 140 is produced in the shape of a hollow container capableof accommodating the molten steel supplied from the ladle 120. An outletdischarging molten steel is formed in the bottom of the tundish 140, sothat the molten steel accommodated in the tundish 140 may be dischargedto the outside through the outlet. The molten steel accommodated in thetundish 140 stays inside the tundish 140 for a period of time, thusbeing poured into the mold 160 after flotation of inclusion contained inthe molten steel.

The mold 160 is provided for shaping the molten steel poured from thetundish 140 in an appropriate size to produce a slab, thus definingwidth and thickness of a passage through which the molten steel passes.The mold 160 of the present invention may be formed such that a slab hasa thickness of 800 mm or less and a width of 2000 mm or less in order tocope with the size of a slab for an extremely thick steel material. Thatis, use of the mold 160 having a greatly increased thickness compared toa mold of a conventional casting installation allows a slab subjected toforging and rolling processes to have a thickness used for the extremelythick steel material.

Meanwhile, there may be provided a guide roll 170 guiding a slab havingan initial shell to the outside of the mold 160 through the mold 160, acooling nozzle (not shown) cooling the slab guided from the guide roll170, and a vibrator (not shown) transmitting vibration to the mold 160so that the slab inside the mold is easily drawn to the outside of themold 160. In the present invention, it is not necessary to particularlylimit the configuration of the guide roll 170, the cooling nozzle, andthe vibrator, but various configurations and operating methods thereofare already widely known to those skilled in the art, so that a detaileddescription thereof will be omitted.

The drawing machine 200 as a machine for drawing a slab from theaccommodation unit 100 to a lower portion, includes: a surface plate 220which is initially disposed inside the mold and receives molten steel toprevent the molten steel from spilling downwards from the mold 160 andconnects the primary solidified slab to an actuator 240, and theactuator 240 drawing the slab to the lower portion.

The surface plate 220 is provided for connecting a slab to the actuator240, and a plate having a specific-shaped surface is used for easyconnection to the slab. Although the present invention does not limitthe shape and the material of the surface plate 220, it is preferablethat the surface plate 200 is made of such a material that does not leadto deformation which may be caused by to a slab of a high temperaturewhen being in contact with the slab.

The actuator 240 is a device for lowering the surface plate 220, and aslab connected to the surface plate 220 may be drawn downwards bylowering the surface plate 220 connected to the actuator 240. Theactuator 240 may employ a device capable of descending to a lowerportion when the slab is drawn and ascending at an initial stage ofcasting so that the surface plate 220 is positioned inside the mold 160.That is, a device capable of descending and ascending may be used as theactuator 240.

The second quality controller 300 is provided for improving quality of aslab drawn from the drawing machine 200 and includes: a stirring unit320 including at least one stirrer disposed on an outside of the mold160 and configured to stir at least any one of molten steel in the mold160 and unsolidified molten steel inside the slab; and a second heater340 installed so as to be able to move forward and backward in a regiondirectly below the mold 160 and configured to heat an upper portion ofthe slab.

The stirring unit 320 is a device having at least one stirrer on anoutside of the mold 160 to improve quality of a slab and includes: athird stirrer 322 disposed in proximity to the mold 160 and able toelevate in a drawing direction of the slab; and a fourth stirrer 324provided spaced apart below the third stirrer 322 and able to elevate inthe drawing direction of the slab. That is, the stirring unit 320 stirsat least any one of molten steel accommodated in a molten state in themold 160 and unsolidified molten steel in the produced slab to performgrain refinement on a slab, thereby being capable of improving qualityof the slab.

As illustrated in FIG. 1, the third stirrer 322 is disposed spaced apartat a predetermined distance from a side of the mold 160, and stirsmolten steel accommodated in the mold 160 during the casting. When thecasting starts, the third stirrer 322 descends by a predetermineddistance along with a slab to stir unsolidified molten steel inside theslab. That is, when molten steel is poured to the mold 160, the thirdstirrer 322 applies an electromagnetic field to the molten steel from aside of the mold 160 to stir the molten steel, and when pouring of themolten steel into the mold 160 is completed, the third stirrer 322 maystir unsolidified molten steel inside a slab while descending to a lowerportion along with the slab. An electromagnetic stirrer (EMS) may beused as the third stirrer 322. The electromagnetic stirrer being able tobe used as the third stirrer 322 typically has a low frequency (Hz) bandcorresponding to a frequency enough to stir molten steel in a moltenstate.

The fourth stirrer 324 is provided spaced apart at a predetermineddistance below the third stirrer 322, and elevates in a drawingdirection of a slab to stir unsolidified molten steel in the slab. Afinal electromagnetic stirrer (FEMS) may be used as the fourth stirrer324. The fourth stirrer 324 is disposed in a relatively lower portioncompared to the third stirrer 322, and it is preferable to use astirring device having a higher frequency (Hz) than the third stirrer322 in order to stir molten steel existing inside a solidified region ina lower portion of a slab (a lower portion from the center with respectto a longitudinal direction of a slab) in which solidification hasprogressed to some extent.

Thus, the stirring unit 320 stirs solidified molten steel in the moldand unsolidified molten steel in the slab, thereby being capable ofenhancing the equiaxed crystal ratio in slab and reducing segregationand porosity. Meanwhile, the present invention does not limit a stirringregion of a slab stirred by the third and fourth stirrers 322 and 324and an elevating width of the stirrers, and various moving ranges may beapplicable according to casting conditions.

The second heater 340 is a device disposed outside of the mold 160 andinstalled so as to be able to move forward and backward in a regiondirectly below the mold (a path in a drawing direction of a slab) toheat an upper portion of the cast slab (tail portion). In thisembodiment, a method according to induction heating (electromagneticheater, EMH) was employed. The second heater 340 indirectly heats theupper side of a slab by using an electromagnetic field generated in aninduction heating coil by power supply, and is wound so as to surroundthe slab while being spaced apart at a predetermined interval from fourdirectional sides of the slab. Thus, the second heater 340 preferablyuses an induction coil having a shape corresponding to a cross-sectionof the slab, but not limited thereto, may be wound in various forms.

Meanwhile, a pusher 400 may be provided to the casting unit 1 a so as totransfer a slab to the solidification unit 1 b after casting of moltensteel is completed.

The pusher 400 is a device disposed in a position facing thesolidification unit 1 b of sides of the casting unit 1 a and pushing aside of a slab and separating the slab from the drawing machine 200 todeliver the slab towards the solidification unit 1 b. A device capableof reciprocally moving a predetermined distance may be used for thepusher 400, and for example, a stepping motor, an actuator, a solenoid,or the like may be used. As an example, when an actuator is used as thepusher 400, a piston reciprocally moves while being inserted and ejectedinto/from a cylinder, thus being able to push the slab toward thesolidification unit 1 b and then return back to an original position. Adevice delivering the slab of the casting unit 1 a to the solidificationunit 1 b is not limited to the pusher 400 and may be a variety ofdevices.

The solidification unit 1 b is a section receiving a slab so as tosolidify the slab cast from the above described casting unit 1 a andincludes: a support unit 500 disposed on at least any one side of theslab to support the slab; and a first quality controller 600 provided onan outside of the slab to induce solidification of the slab. Thesolidification unit 1 b receives the slab from a section spaced apart ata predetermined distance from the casting unit 1 a, completessolidification of the slab, and then transfers the slab to apost-process (for example, forging or rolling).

The support unit 500 is provided so that the slab is stably positionedin the solidification unit 1 b and includes: a support block 520disposed in contact with the bottom of the slab; and a support frame 540disposed surrounding a portion of a side of the slab. However, theconfiguration of the support unit 500 is not limited thereto, but theslab may be supported by a variety of devices and methods within theextent not interfering with the movement of the first quality controller600.

The supporting block 520 uses a block in a shape similar to the surfaceplate 220 of the casting unit 1 a. The support block 520 plays a role ofsupporting a lower portion of the slab disposed in the solidificationunit 1 b in a drawing direction, i.e. a longitudinal direction.

The support frame 540 may be disposed spaced apart at a predetermineddistance from a side of the slab and surrounding a portion of a side ofthe slab so as to suppress and prevent the slab disposed in thelongitudinal direction from falling, as illustrated in an enlarged viewin FIG. 1.

The first quality controller 600 as a device provided on an outside of aslab and to ensure slab quality includes: a first stirrer 620 disposedin proximity to an outside of the slab and able to elevate in alongitudinal direction of the slab; a second stirrer 640 provided spacedapart below the first stirrer 620 and able to elevate in thelongitudinal direction of the slab; and a first heater 660 configured toheat an upper portion of the slab. That is, since solidification of theslab which is naturally cooled is not completed, the first qualitycontroller 600 may be provided with a device the same as or similar tothe casting unit 1 a to continue a treatment process for improving slabquality.

The first stirrer 620 as a device for stirring unsolidified molten steelin a slab delivered to the solidification unit 1 b is disposed spacedapart at a predetermined distance from the slab. The first stirrer 620may be installed so as to be able to elevate in such a way that thefirst stirrer 620 descends to be disposed on a side of the slab when theslab is delivered to the solidification unit 1 b with the first stirrer620 being disposed at the same height as or a similar height to thethird stirrer 322. The first stirrer 620 is disposed in an upper portionoutside of the slab. That is, the first stirrer 620 is disposed abovethe center of the slab with respect to a longitudinal direction of theslab. An unsolidified region in an upper portion of the slab, which isstirred by the first stirrer 620, is subjected to relatively lessprogressed solidification than a lower portion of the slab, so that alarge amount of unsolidified molten steel is included in the slabcompared to the lower portion of the slab. Thus, an electromagneticstirrer (EMS) similar to the third stirrer 322 may be used.

Meanwhile, although the first stirrer 620 uses a device similar to thethird stirrer 322, the first and third stirrers 620 and 322 may bedifferent in the size of a frequency generated thereby or the operatingtime thereof from each other. That is, the third stirrer 322 stirsmolten steel in the mold 160 or molten steel in an initial slabsubjected to solidification, and thus uses a frequency less than about 1Hz. The third stirrer 322 operates during the following processes:pouring of molten steel into the mold 160, casting the molten steel intoa slab, and transferring of the slab to the solidification unit 1 b. Inthe case of the first stirrer 620, due to a characteristic of the slabtransferred to the solidification unit 1 b, the slab is not providedwith the mold and forms a thicker solidified shell compared to the slabcast in the casting unit. Therefore, the first stirrer 620 uses afrequency of up to 5 Hz and operates until the casting of the slab iscompleted so that the magnetic field of the first stirrer 620 passesthrough the thickened solidified shell to stir unsolidified molten steelin the slab. However, solidification of a slab occurs in a wide varietyof forms according to casting situations and casting conditions, so thatthe third and first stirrers 322 and 620 may use a frequency in a rangeof 0 to 5 Hz according to various operation patterns. In addition, thefirst stirrer 620 disposed in the solidification unit 1 b in FIG. 3Dstirs unsolidified molten steel in the slab to equalize temperatures ofunsolidified molten steel in the slab during solidification of the slabin the solidification unit 1 a, thus being able to operate veryefficiently in reducing pipe defects inside the slab in such a way thatthe first heater 660 heats an upper side of the slab to prevent an upperportion of the slab from being pre-solidified. Similarly, the thirdstirrer 322 disposed in the casting unit 1 a in FIG. 3F stirsunsolidified molten steel in the slab to equalize temperatures ofunsolidified molten steel in the slab during solidification of the slabin the casting unit 1 a, thus being able to operate very efficiently inreducing pipe defects inside the slab in such a way that the secondheater heats an upper side of the slab to prevent an upper portion ofthe slab from being pre-solidified.

The second stirrer 640 is provided spaced apart at a predetermineddistance below the first stirrer 620 and installed so as to elevate in alongitudinal direction of a slab to stir unsolidified molten steel inthe slab. That is, the second stirrer 640 is disposed below the centerof the slab with respect to a longitudinal direction of the slab.Although the second stirrer 640 may use a final electromagnetic stirrer(FEMS) similar to the fourth stirrer 324 so as to stir unsolidifiedmolten steel in a lower region outside of the slab, the second andfourth stirrers 640 and 324 may be different in the size of a frequencygenerated thereby or the operating time thereof from each other. Thatis, the fourth stirrer 322 uses a frequency of up to about 3 Hz so as tostir unsolidified molten steel in the slab which is being solidified inthe casting unit 1 a. The fourth stirrer 324 operates before the slabcast in the casting unit 1 a is transferred to the solidification unit 1b. In the case of the second stirrer 640, due to a characteristic of theslab transferred to the solidification unit 1 b, the slab forms athicker solidified shell compared to the slab cast in the casting unit.Therefore, the second stirrer 640 uses a frequency of up to 6 Hz andoperates until the casting of the slab is completed. However,solidification of a slab occurs in a wide variety of forms according tocasting situations and casting conditions, so that the fourth and secondstirrers 324 and 640 may use a frequency in a range of 0 to 6 Hzaccording to various operation patterns.

Meanwhile, in the embodiment, although the first and second stirrers 620and 640 are provided in plurality to respectively stir unsolidifiedmolten steel in different regions of the slab, an apparatus and a methodfor stirring unsolidified molten steel in the slab in the solidificationunit 1 b are not limited thereto. That is, the embodiment may bemodified to various methods and apparatus shapes in such a way that asingle stirrer is provided and a whole region from an upper portion to alower portion of the slab may be stirred while the frequency of thestirrer is being changed.

Thus, the first and second stirrers 620 and 640 stir molten steel untilsolidification of the slab transferred to the solidification unit 1 b iscompleted, thus being able to enhance the equiaxed crystal ratio in theslab and improve slab quality by reducing segregation and porosity as inthe stirring unit 320 of the casting unit 1 a.

Meanwhile, in the case of the third and first stirrers 322 and 620applied to the present invention, in order to ensure a uniform stirringforce in molten steel in the slab according to significantly increasedsizes compared to molds applied to existing continuous casting machines,coils wound around the mold 160 or the slab were disposed in the form ofa circle to perform rotation-type stirring on unsolidified molten steelin the mold or the slab.

The first heater 660 is a device installed so as to be able to moveforward and backward in a direct upper region of slab for heating anupper portion of the slab in an outside of the slab and configured toheat an upper portion (tail portion) of the slab transferred to thesolidification unit 1 b. Since the first heater 660 has similarconfiguration and effect as in the second heater 340, a detaileddescription thereof will not be repeated.

The above described casting installation 1 may include a transfer unitwhich transfers the slab from the casting unit 1 a to the solidificationunit 1 b and/or from the solidification unit 1 b to the outside of thesolidification unit 1 b, i.e. a post-process.

The transfer unit 700 is a device disposed on one side of thesolidification unit 1 b and formed so as to be able to move forward andbackward toward the casting unit or the solidification unit to transferthe slab. The transfer unit 700 includes: a tilting unit 720 for tiltingthe slab in contact with the slab in the casting unit 1 a ortransferring the slab from the casting unit 1 a to the solidificationunit 1 b; and a driving unit 740 controlling operation of the tiltingunit 720.

The tilting unit 720 is disposed on one side of the slab and transfersthe slab while being tilted or moved forward and backward by the drivingunit, and the support block 520 of the solidification unit 1 b isconnected to transfer the slab. That is, the slab may be transferredfrom the casting unit 1 a to the solidification unit 1 b in such a waythat one side of the tilting unit 720 is connected to the support block520 supporting the slab and the slab is disposed on the support block520. When the slab is transferred from the solidification unit 1 b tothe outside of the solidification unit, the tilting unit 720 is tiltedwith the slab being in contact with one side of the tilting unit 720 andthe slab may be seated on the tilting unit disposed in the transferringdirection. On a side in which the tilting unit 720 contacts the slab, aroller 725 may be mounted to easily transfer the slab.

The driving unit 740 controls operation of the tilting unit 720, and mayallow the tilting unit 720 to move forward and backward so that thetilting unit 720 approaches or recedes from the casting unit 1 a. Inaddition, the driving unit 740 allows the tilting unit 720 to be tiltedand communicate with a roller table 800 guiding the tilting unit 720 andthe slab to a post-process. A device such as the pusher 400 of thecasting unit 1 a capable of reciprocally moving a predetermined distancemay be used for the driving unit 740, and for example, when an actuatoris used, the tilting unit 720 may be connected to an end of a piston soas to enable angle adjustment.

In this way, in this embodiment, although the method and device asdescribed above are used for the transfer unit 700 transferring theslab, the device and operating method used for the transfer unit 700 arenot limited thereto, and various devices and methods capable of easilytransferring the slab may be used when the slab is transferred from thecasting unit 1 a to the solidification unit 1 b or from thesolidification unit 1 b to a post-process.

Hereinafter, a casting method using the above-described castinginstallation will be described.

Referring to FIG. 2, a casting method according to an embodiment of thepresent invention includes: providing molten steel to prepare casting;casting the molten steel in a casting unit allowing a passage throughwhich the molten steel passes to be opened or closed; and transferring aslab produced through the casting to a solidification unit.

First, molten steel after refining is completed is accommodated in aladle 120 and then transferred to the casting unit so as to startcasting. The molten steel transferred to the casting unit is supplied tothe tundish 140 from the ladle 120, flotation of inclusion is thenperformed in the tundish 140 for a period of time, and the molten steelis then poured to the mold, thereby performing the process in thecasting unit 1 a (S100). As illustrated in FIGS. 3A to 3F, preparationof the casting is competed in a condition in which the surface plate 220is positioned in a mold to prevent molten steel poured to the mold 160from being discharged to the outside (S120).

After the preparation of the cast is completed, as illustrated in FIG.3B, as the drawing machine 200 operates to lower the surface plate 220down and a slab S1 connected to the surface plate 220 is drawn downwardsto start the casting, slab is produced (S140). Before the castingstarts, the third stirrer 322 is operated to stir molten steel in themold. The slab is produced in a size of a maximum thickness of 800 mm, amaximum width of 2000 mm, and cast at a casting rate of 0.3 m per minuteor less. By a characteristic of an extremely thick steel material, themold 160 in which a slab has an increased thickness needs to be used soas to obtain a final product having an increased thickness. A reason whythe slab is cast at a low casting rate of 0.3 m per minute is thatsuppressing occurrence of segregation to secure internal quality bycasting at a slow casting rate and securing a sufficient thickness ofthe solidified shell during casting are required as a solidificationrate of a slab for the extremely thick steel material is slow unlike ageneral slab.

While the casting is in progress, the third stirrer 322 continuallystirs molten steel in the mold and the fourth stirrer 324 continuallystirs unsolidified molten steel inside the slab so that solidificationproceeds by characteristic of thick slab. Thus, the third and fourthstirrers 322 and 324 may refine a structure of slab by continuouslystirring molten steel to enhance quality and equiaxed crystal ratio ofslab.

When the casting is complete on the casting unit 1 a (S160), the slab S1located in the casting unit 1 a is separated from the surface plate bythe pusher 400 and supported by the transfer unit 700 to move to thesolidification unit (S200). When a pushing force is delivered to theslab S1 by the pusher 400, the slab S1 may be transferred to thesolidification unit 1 b in a state solidification of a surface isadvanced to a degree of no deformation. Meanwhile, the stirring unit 329moving upper and lower portions in the casting and solidifying slabreturns to its original position so as not to interfere with transfer ofthe slab S1.

After the slab is transferred to the solidification unit 1 b, a processof finally completing solidification of the slab S1 proceeds in thesolidification unit 1 b (S300). That is, since the slab S1 is solidifiedin the solidification unit 1 b, a casting process may be performed inthe casting unit 1 a. When solidification of the slab S1 starts, thefirst quality controller 600 provided in the solidification unit 1 bdescends or ascends to be disposed spaced apart from an outside of slab.That is, as illustrated in FIGS. 3A to 3F, the first and second stirrers620 and 640 are disposed outside of the slab for stirring unsolidifiedmolten steel inside the slab S1 to operate until solidification of theslab S1 is completed.

In a process of solidifying the slab, the first heater 660 indirectlyheats an upper portion of the slab inside each of regions to solidifyingthe upper portion of slab while heat is suppressed from being releasedfrom a side of the upper portion of the slab as much as possible. Thismay suppress or prevent unsolidified region of an upper portion of theslab from being pre-solidified by indirectly heating a side of an upperportion of the slab to minimize a solidification shrinkage defect suchas a pipe. Thus, yielding percentage of slab is enhanced to improveyielding percentage of a final slab.

Thus, when solidification of the slab is completed in the solidifiedportion 1 b, S340, as illustrated in FIG. 3E, the slab is tilted by thetilting unit 720 of the transfer unit 700 and the tilting unit 720 ofthe transfer unit 700 is connected to the roller table 800 disposed invicinity of the transfer unit 700 and the slab is transferred to apost-process along the roller table 800.

Thus, the process of FIGS. 3A to 3F is not limited to a number of timesand may be repeated. As illustrated (b) in FIG. 2, after a process ofthe casting unit 1 a is completed, a process of the casting unit 1 a isre-processed in the casting unit 1 a and produces another slab S2 to beable to be repeated until obtaining required quantity while the slab S1is transferred to the solidification unit to perform a process of thecasting unit (slab solidification process).

When the process of the casting unit 1 a no longer proceeds afterrepeating the above described process, that is, the last slab Se isproduced in the casting unit 1 a after the slab S2 in FIG. 3E istransferred to the solidification unit 1 b, the slab Se in the castingunit 1 a may finish solidification in the casting unit 1 a without beingtransferred to the solidification unit 1 b. That is, the slab Sefinishes solidification by using the second quality controller 300provided in the casting unit 1 a and then may be transferred to apost-process (S360). The second heater 340 of the casting unit 1 aindirectly heats an upper portion of the slab Se to perform a role ofthe first heater 660 of the solidification unit 1 b. However, the lastproduced slab Se may be transferred to a post-process after beingtransferred to the solidification unit 1 b and then completing asolidification process as similarly as the previously produced slabs S1and S2. Thus, a position of the final slab Se is not limited.

Hereinafter, effects of the present invention will be described in moredetail through experimental examples.

Table 1 shows the results of changes in slab thickness and yieldingpercentage of a finally produced slab in a variety of process conditionsfor producing the extremely thick steel material.

TABLE 1 Slab thickness (mm) Yielding Initial stage Middle stage Finalstage percentage (%) Comparative 1500 300 178 52 Example 1 Comparative450 — 150 95 Example 2 Example 800 300 178 89

Herein, the slab thickness of the initial stage indicates the thicknessof the slab when an additional post-process is not performed on the slabof a completed cast. In addition, the slab thickness of the middle stageindicates the thickness of the slab after a forging process beating orpressing the slab and, the slab thickness of the final stage indicatesthe thickness of the slab after a rolling process.

Each of the slabs (Comparative Example 1, Comparative Example 2,Example) shown in Table 1 are slabs produced as a slab for the extremelythick steel material after undergone a casting process and then at leastany one of a forging or a rolling process, and Table 1 may showfollowing results as below.

Comparative Example 1

The slab in Comparative Example 1 is produced through an ingot process,thus being able to be obtained by supplying molten steel to a mold andcooling the molten steel. The slab produced as above has an initialthickness of about 1500 mm. Then, the slab finally has a thickness ofabout 178 mm after undergone a forging and rolling process so as to forma thickness for the extremely thick steel material. However, it may beconfirmed that a total yielding percentage has a low value of about 52%.

Comparative Example 2

The Slab in Comparative Example 2 is produced through a normal castinginstallation, thus being able to be produced by continuously pouring andsolidifying molten steel supplied from a steelmaking plant to a mold.

The slab in Comparative Example 2 is produced through a normal castinginstallation, thus being able to be produced by continuously pouring andsolidifying molten steel supplied from a steelmaking plant to a mold.The slab produced as above has very high yielding percentage of about95%. However, in a generally used casting installation, the slab isproduced to have an initial thickness of about 450 mm, thus having athickness about 150 mm after a rolling process is completed. Thus, itmay be confirmed that the slab is limited to have a thickness of about150 mm when used for the extremely thick steel material.

Example

The slab in Example is produced through a casting installation accordingto an embodiment of the present invention, thus being produced throughthe slab having a maximum thickness of about 800 mm and a maximum widthof about 2000 mm. Thus, the slab in Example produced to have an initialthickness of about 800 mm and may be confirmed to finally have athickness of about 178 mm after undergone a forging and rolling process.In addition, since the casting installation is separated into a castingunit and a solidification unit and a process for preventingpre-solidification of an upper portion of the slab is performed, theslab in Example is confirmed to have a yielding percentage of about 89%.

As such, the slab in Example has a yielding percentage significantlyenhanced by about 40% when compared to the slab of Comparative Example 1and a thickness suitable for the extremely thick steel material whencompared to the slab in Comparative Example 2. That is, the slabproduced by the installation in Example may solve problems of a slabproduced through an ingot casting and a conventional continuous casting.

In addition, the extremely thick steel material produced according tothe embodiment was not observed to have a surface defect (for example, acorner crack) identified by a naked eye and segregation generated insidethe slab as macro quality achieved equiaxed crystal ratio of 100% byapplying a molten steel stirrer to the slab. Accordingly, it may beconfirmed that the extremely thick steel material produced according tothe embodiment of the present invention is improved.

As described above, according to the embodiment of the presentinvention, since a continuous casting installation is separated into thecasting unit and the solidification unit and the slab in which castingis completed in the casting unit is transferred to the solidificationunit and the slab in which solidification is completed in thesolidification unit is transferred to a post-process, the extremelythick steel material may be easily produced and quality and yieldingpercentage of the slab finally produced may be improved.

More specifically, since the slab produced in a casting unit istransferred to the solidification unit and then solidification of theslab is completed through the first quality controller andpre-solidification of an upper portion of the slab is suppressed orprevented to reduce formation of pipe, quality of the slab may beenhanced. Therefore, since cutting unsound region that is a problem ofan ingot casting is not performed due to improved slab quality, yieldingpercentage of the slab may be enhanced.

In addition, since the next slab may be cast in the casting unit whilethe slab is transferred to the solidification unit and then solidifiedin the solidification unit, a problem of a batch process such as aconventional continuous casting may be solved. Thus, as a result,productivity of the slab may be increased. Further, the slab produced ina last casting process is not transferred to the solidification unit andsolidification of the slab may be completed through the second qualitycontroller provided in the casting unit. Thus, process efficiency may beimproved.

The present invention will now be described more fully with reference tothe accompanying drawings, in which exemplary embodiments of theinvention are shown. The present invention is limited not thereto andbut by Claims. Moreover, various changes and modifications within thescope not departing from the basic principles of the present inventionare possible to those skilled in the art of the present invention.

What is claimed is:
 1. A casting installation comprising: a casting unitdefining a passage through which molten steel passes and for casting themolten steel into a slab; and a solidification unit comprising: asupport unit disposed spaced apart from the casting unit and receivingthe slab from the casting unit and disposed on at least any one place ofsides of the slab to support the slab; and a first quality controllerprovided on an outside of the slab to induce solidification of the slab.2. The casting installation of claim 1, wherein the first qualitycontroller comprises: a first stirrer disposed in proximity to anoutside of the slab and able to elevate in a longitudinal direction ofthe slab; a second stirrer provided spaced apart below the first stirrerand able to elevate in the longitudinal direction of the slab; and afirst heater installed so as to be able to move forward and backward ina region directly above the slab and configured to heat an upper portionof the slab.
 3. The casting installation of claim 2, wherein the firststirrer has coils wound around the slab and disposed in the form of acircle.
 4. The casting installation of claim 1, wherein the casting unitcomprises: an accommodation unit having a space in which the moltensteel is accommodated; a drawing machine drawing the slab from theaccommodation unit to a lower portion; and a second quality controllerprovided on an outside of the passage.
 5. The casting installation ofclaim 4, wherein the accommodation unit comprises a mold configured toform the passage through which the molten steel supplied to a tundishpasses, and the mold is formed so that the slab has a thickness of 800mm or less and a width of 2000 mm or less.
 6. The casting installationof claim 4, wherein the second quality controller comprises: a stirringunit comprising at least one stirrer disposed on an outside of the moldand configured to stir at least any one of the molten steel andunsolidified molten steel inside the slab; and a second heater installedso as to be able to move forward and backward in a region directly belowthe mold and configured to heat an upper portion of the slab.
 7. Thecasting installation of claim 6, wherein the stirring unit comprises: athird stirrer disposed in proximity to the mold and able to elevate in adrawing direction of the slab; and a fourth stirrer provided spacedapart below the third stirrer and able to elevate in the drawingdirection of the slab.
 8. The casting installation of claim 7, whereinthe third stirrer has coils wound around the mold or the slab anddisposed in the form of a circle.
 9. The casting installation of claim1, wherein a pusher for separating the slab from the drawing machine isprovided to the casting unit and the pusher is installed so as to beable to reciprocally move forward and backward toward the solidificationunit.
 10. The casting installation of claim 1, wherein a transfer unittransferring the slab from the casting unit to the solidification unitor from the solidification unit to an outside of the solidification unitis provided.
 11. A casting method comprising: providing molten steel toprepare casting; casting the molten steel in a casting unit allowing apassage through which the molten steel passes to be opened or closed;transferring a slab produced through the casting to a solidificationunit; and transferring the slab to a post-process after solidificationof the slab is completed.
 12. The casting method of claim 11, whereinthe casting of the molten steel is repeated in the casting unit afterthe slab is transferred to the solidification unit.
 13. The castingmethod of claim 12, wherein, when the casting of the molten steel isrepeated, the transferring the slab to the solidification unit isperformed while the molten steel is transferred to the casting unit sothat preparing the casting is performed.
 14. The casting method of claim11, wherein when the casting of the molten steel is a single casting,that is one time casting, the solidification of the slab is completed inthe casting unit or after the slab is transferred to the solidificationunit.
 15. The casting method of claim 11, wherein the molten steel iscast at a casting rate 0.3 m per minute or less.